The jump created a dramatic spread of 11.45 percentage points between the average credit card interest rate and the prime rate -- the largest margin in 22 years, according to Synovate.

Synovate study director Lauren Guenveur said the increase in interest rates was driven primarily by the Credit Card Accountability Responsibility and Disclosure Act of 2009. She said the so-called CARD Act gave credit card companies a limited amount of time to raise rates, "before they could no longer do so freely." This put pressure on issuers to aggressively raise rates, she said.

Guenveur added that the recession and nation's high unemployment were also driving the increase, because it was causing the default rate to go up.

"This is largely due to consumers still charging on their credit cards, but being unable to pay," she said. "Default rates should remain high as long as unemployment remains high."

Synovate spokeswoman Jennifer Chhatlani also attributed the rate increase to "returning confidence" in the credit card sector. The second quarter of 2010 saw the second-highest level of credit card spending ever, Synovate said.

Synovate reported that credit spending has increased, on average, by 6% in the first half of 2010 to $1,559. But plastic swipes still fall short of third quarter 2008 numbers, which Synovate describes as "the quarter prior to the financial meltdown."

The credit card industry has taken notice of the increase in activity. Offers for new cards reached a fever pitch last quarter. U.S. households received 640.3 million credit card offers in the second quarter, a surge of 83% from 349.1 million offers during the same period last year.

"Issuers are desperate to lock-in customers with good credit, so they will mail many offers to these households in order to gain their attention," Guenveur said.

She said direct mailing is the most expensive way to advertise, and has decreased in the last couple years. But now direct mailing is pulling out of its slump.

"As the economy recovers, issuers have released the pause button and started to spend money on direct-mail marketing again," she said.